Definition of "lobster"

Red-colored, especially from a sunburn.  examples

A crustacean of the Nephropidae family, dark green or blue-black in colour turning bright red when cooked, with a hard shell and claws, which is used as a seafood.  quotations  examples

A crustacean of the Palinuridae family, pinkish red in colour, with a hard, spiny shell but no claws, which is used as a seafood.  examples

(slang, historical) A soldier or officer of the imperial British Army (due to their red or scarlet uniform).

(slang) An Australian twenty dollar note, due to its reddish-orange colour.

To fish for lobsters.  examples

(Internet slang) To trick someone with a blue lobster picture and an annoying Toccata and Fugue in D minor.